I've been playing for a few months now and love the game. Recently I've been doing great with a Daoloth team(a second Daoloth, Honor, Tulzscha, Fafnir as the teammates), but I have been finding it a bit tough clearing the truly high level stuff with this team.

Today I pulled a Xi and was really excited and even maxed her immediately, but she doesn't seem to be a great leader, she definitely doesn't have the pop of my Daoloth team.

Then I read about the Greeks... I actually have a Hephaestus buried away in my box, and am now wondering if I should spend the time/resources on leveling him up. I don't have any Zeus cards, which I see in Hephaestus's team notes, so I'm not sure if that would hurt the team. I don't have a ton of fire gods, but I do have Heimdallr, Amaterasu and Skeggjald. Would it be worth it to use those cards on a Hephaestus team with another random fire card along for the ride? Or should I just stick with Daoloth until I get some other fire gods? I'd really love any and all input, thanks in advance!

Xi is bugged at the moment, so if you're not feeling her, you might wanna try her again in a patch's time when her leader skill actually works.

Hephaestus is the only Greek I have right now, he seems... okay. The damage is not what I thought it would be but I don't have the best fire god pool for members either. I think a lot of people are using him with Shakuro (Fire Dragon) though because she transforms him into a high combo, high recovery team, which is the aspect of him that I think is actually the strongest. I'd love to have Heimdallr like you though... also Fire Bride, but that's a pipe dream at the moment.

I think very few leaders in the game are capable of blowing through content with minimal member support and Daoloth is one of them.

VR Xi and VR Heph, imo, will need the support of a good member roster, much more than Daoloth does. OVR Xi running with NVR Xi and/or Wen Zhong as members, for example.

VR Heph doesn't need to be god only (the god runes are only a fraction of total fire rune dissolve which reduces the difference in damage), but I think a lot of his power comes from the triple penalty-less enchantress combo of OVR Fire Bride, Kyo, and Shakuro pretty much giving you free constant damage boosts and ultra recovery. Even without using Shakuro, VR Heph's recovery is very impressive for a fire team (by which I mean actually capable of a full heal with a set of hearts). You've also got Piasa for permanent damage reduction, Medea for another 2x, etc so VR Heph has access to a lot of good permanent effects.
I don't have Kyo, but I've been running Fire Bride+Medea or Fire Bride+Shakuro with good results.
From trying NVR Fire Bride, I personally don't think Heimdallr or NVR Fire Bride gives enough of a consistent damage boost to be worth the trouble of using, but people may have different opinions.

I'd want to see what you have for fire other than gods, because the fire god roster in the game is not amazing enough to just run mono-fire god, especially considering the gameplay of VR Heph rules out or lowers the effect of a lot of members. A lot of fire gods are big fire converters and VR Heph's damage actually suffers the more you convert. Amaterasu is a good stall, but you won't get a big damage boost from the god runes, since your initial runes are a small fraction of total rune damage, etc.

Medea (Kolchis) works because even a 2x multiplier on a team that makes as many combos as VR Greeks is valuable. Fthaggua is decent, fast burst. Then Heim and Skegg? You're sacrificing recov for damage with that setup though, but Skeggjald kind of works as a defensive card. It's not the best, but there's not many options. The new Zeus should be along shortly and he'll probably be a decent member.

Doris (Red Hood), too. Farmable to slvl10 with Fire Golems from the Lost Relic Pass Registry, min CD 6 at slvl 12. The conversion only removes 1 attribute from the board, so for a speedy 2.2x burst, I think it's a fair trade.

Piasa also works for permanent defense (he can also help mitigate Medea's 1.5x penalty), but it's kind of an expensive investment at slvl 15 with no feeders, so it really depends on your resources. I'd say Piasa is potentially useful, but low priority.

Amaterasu and Meng Hou can be swapped in as the stage requires for utility purposes (stalling/defense piercing/unlocking weakening runes, removing masked boards, etc).

Using Heimdallr in this team is pretty risky, not sure I'd recommend him as a permanent member.

Alright, this is super helpful! I really do appreciate it, you guys are incredibly knowledgeable, reading your suggestions helps me put plans together instead of just bumbling through the game like I usually do. I definitely have a lot of work to do before I have a functional Hephaestus team, but at least now I have a few directions to go. Now I'm off to VR Hephaestus. Even though I can't really use him right away, I can show him off with pride as my adjutant!